Field of the Invention
The present invention relates to a coating apparatus used for a photoresist (PR) or organic material coating process among liquid crystal display (LCD) manufacturing processes, and more particularly, to a coating apparatus capable of managing a front end of a nozzle without priming and a method of forming a coating layer using the coating apparatus.
Discussion of the Related Art
In general, a process of manufacturing a liquid crystal display module employing a thin film transistor (TFT) is divided into a TFT process, a cell process, and a module process.
In the TFT process, a TFT is repeatedly formed in an array on a glass substrate. The TFT process includes a plasma enhanced chemical vapor deposition (PECVD) process of introducing a gas required for deposition into a vacuum chamber, and transforming the introduced gas into plasma using radio frequency (RF) power to perform deposition on the substrate when pressure and substrate temperature are set, a sputtering process in which gaseous ions having high energy in plasma formed by RF power or direct current (DC) power collide with a target surface, and atoms to be deposited are sputtered from the target and deposited on the substrate, a photolithography process of selectively radiating light to a PR using a mask having a desired pattern to form the same pattern as the mask pattern according to a principle that when a photosensitive chemical (e.g., PR) reacts with light, its properties are changed, and an etching process using a phenomenon that a reactive material such as atoms or radicals produced from gas plasma reacts with the material deposited on the substrate and is converted into a volatile material.
The cell process includes an alignment layer deposition process of forming alignment layers on a lower substrate on which a TFT is formed and an upper substrate on which a color filter is formed, a rubbing process of causing liquid crystals to be aligned on the alignment layer, a spacer process of dispensing spacers, and a liquid crystal injection process of attaching the upper substrate and the lower substrate to each other, injecting liquid crystals thereinto, and then sealing an injection hole.
In the module process, a quality of a product finally provided to a user is determined. In this process, a polarizing film is attached to a completed panel, a driver integrated circuit (IC) is mounted, a printed circuit board (PCB) is assembled, and finally a backlight unit and a chassis are assembled.
In the photolithography process of the TFT process among these LCD manufacturing processes, light is selectively radiated to a PR which reacts with light to have a changed property through a mask having a desired pattern, thereby forming the same pattern as the mask pattern.
Such a photolithography process is carried out in order of a PR coating operation of coating a deposited thin film, that is, a glass surface, with a PR, an exposure operation of selectively radiating light using a mask, and a development operation of removing the PR in an illuminated portion using a developer to form a pattern.
Among coating apparatuses used for PR coating in the PR coating operation, a “spinless coater” includes, as shown in FIG. 1, a coater chuck 10 for fixing a glass G, a nozzle 12 for spraying a PR solution while moving over an upper surface of the glass G fixed by the coater chuck 10, and a cleaning unit 20 for cleaning the nozzle 12.
As shown in FIG. 2, the cleaning unit 20 is in the form of one module composed of a cleaner 22, a priming roller 24, and a standby unit 26, and is disposed on one side of the coater chuck 10.
Such a coating apparatus operates in a normal mode in which the nozzle 12 repeatedly sprays a PR solution and an idling mode in which the nozzle 12 temporarily stops spraying the PR solution. Operations of the nozzle 12 according to the modes will be described below.
First, in the normal mode, a coating process in which the nozzle 12 sprays a PR solution to the surface of the glass G to perform PR coating, a cleaning process in which, after the coating operation for the one glass G is finished, the nozzle 12 returns to the cleaning unit 20 and is cleaned in the cleaner 22, and a preparation process in which the PR solution of the nozzle 12 is dispensed by the priming roller 24 to enter a spray preparation state are performed in sequence. After the preparation process, the coating process is repeated so that coating operations for a plurality of glasses are continuously carried out.
In the preparation process for the spray preparation state, the PR at the front end of the nozzle 12 may be dried until the next glass is prepared after the one glass G is coated, and thus the PR solution is dispensed little by little. Such a PR dispensation also prevents a cleaning solution from entering the nozzle 12 while cleaning is performed by a mobile cleaner 23.
In the cleaning process, the mobile cleaner 23 installed at the cleaner 22 moves and cleans the nozzle 12.
In the idling mode, after the nozzle 12 having finished the coating process undergoes a cleaning process and a preparation process, it is moved to the standby unit 26 and undergoes a standby process of being dipped into a PR solution P contained in the standby unit 26. After a predetermined time, the cleaning process is performed again.
In other words, in the idling mode, the nozzle 12 is dipped into the PR solution P during the standby process to prevent the PR solution remaining in the nozzle 12 from being completely dried and to smoothly perform a restarted coating process.
The dipping operation is performed by moving the nozzle 12 up and down. This is enabled because the nozzle 12 has an operation structure capable of moving up and down due to the characteristics of spinless coating that a PR dispensing operation should be precisely performed.
However, the conventional spinless coater including such a cleaning unit has some problems. The PR may be dried on the outside of the nozzle 12 dipped in the idling mode and hinder a nozzle cleaning operation. Also, the PR solution P contained in the standby unit 26 may become hard and cause problems. Furthermore, it is difficult to maintain an appropriate amount of PR in the standby unit 26.
Lately, substrates have become larger and are damaged by even a small impact. To prevent such damage, substrates are floated and conveyed in the air, and a method of performing each unit process with a substrate floated over a stage not to contact the stage surface is under research. For this reason, coating apparatuses require an air-floating stage, and are required to form a coating layer with a substrate floated in the air.